Support for end-to-end voice calls using Internet Protocol ("IP") networks such as the Internet as an alternative to traditional public switched telephone networks ("PSTN") is well known. Unlike the PSTN, which is circuit-switched, the Internet is packet-switched; communication on the Internet is accomplished by transmitting and receiving packets of data. In addition to data, each packet contains a destination address to ensure that it is routed correctly. The format of these packets is defined by the IP. One type of allowable data is encoded, digitized voice, termed voice over IP (VoIP). VoIP is voice that is packetized as defined by IP, and communicated over the Internet for telephone-like communication. Individual VoIP packets may travel over different network paths to reach the final destination where the packets are reassembled in correct sequence to reconstruct the voice information.
While transmission over the Internet is inexpensive relative to transmission over the PSTN, the Internet poses problems which are not present in the PSTN. In particular, the transmission speed between any two users can change drastically due to the dynamic number of users sharing the common transmission medium, their bandwidth requirements, the capacity of the transmission medium, and the efficiency of the network routing and design. Other problems associated with VoIP are the variability of the quality of the signal received at the destination (i.e. the number of transmission errors such as packet loss, packet delay, corrupted packets, etc.). Thus, while the Internet may be a suitable medium for voice communications the suitability is not consistent.
Many businesses employ customer premise switches ("CPS")(e.g. Key Signaling Units ("KSU"), Private Branch Exchanges ("PBX"), Centrexes or the like) for routing calls, inter alia, from the business equipment to destination telephone equipment. When an end-user makes a call, the digits dialed are parsed based upon pre-configured tables which indicate which communication interfaces are to be employed for the call attempt (i.e. PSTN, Internet, other IP networks, etc.). The choice of which route to take may be based upon cost or quality of the connection or other well known attributes. In addition to routing calls through the PSTN, many of these CPS route calls through unreliable networks such as the Internet, Frame Relays and the like.
Systems currently exist which monitor the quality of service (QoS) of an unreliable network to determine if an alternate communication path should be chosen. However, such systems either disable the gateway to the network when the QoS falls below a predetermined threshold, the call manager associated with the network routes the call back to the routing engine to be rerouted therefrom or the call manager routes the call to an alternate network.
Disabling the gateway entirely is illogical since the QoS of the network is specific to a destination. Thus while the QoS of the network with regard to one destination may not be acceptable, the QoS of the network with regard to other destinations may be acceptable. Thus, disabling the entire gateway shuts off a relatively inexpensive route for all calls when only a single destination may be unusable. With regard to either routing the call from the call manager back to the routing engine or routing the call from the call manager to another network, this wastes valuable resources (e.g. communication channels, etc.).
Accordingly, there exists a need for a customer premise switch ("CPS"), having access to an unreliable network for routing calls, which can determine the QoS of the unreliable network for a particular call prior to routing the call to the call manager for that network.
Accordingly, it is an object of this invention to provide a CPS, having access to an unreliable network for routing calls, which can determine the QoS of the unreliable network for a particular call prior to routing the call to the call manager for that network.
This and other objects of the invention will become apparent to those skilled in the art from the following description thereof.